Battery chargers can be classified into two general groups; linear regulator battery chargers and switching regulator battery chargers. Conventional linear regulator battery chargers typically employ single stage charge control with hardware-based voltage regulation. The use of hardware-based voltage-regulation limits the flexibility of the control scheme. For example, during input overvoltage conditions conventional chargers must be shutdown to protect the charging components from overdissipation. In addition, linear regulator battery chargers require an external current limit to protect the battery from a charger fault condition that could result in excessive current being supplied to the battery. The external current limit circuit generally requires tight voltage regulation to ensure that the current is limited to below a level that could damage the battery.
While conventional battery chargers can be used to charge batteries during normal operating conditions, they have proven to be deficient during abnormal operating conditions such as input overvoltage and battery overcurrent conditions.